Polycarbonates and other soluble polymers, copolymers and polymer combinations (hereinafter collectively referred to as "polymers") are used extensively for a variety of industrial and consumer product applications including automobile parts, compact discs, and roadway signs to name a few. In a pure, clean unformulated state, soluble polymers may be used for any number of applications. Once a polymer is designated for a product application, the polymer encounters incorporation of colorants, formulations and other additives to yield a desired property package, processing consistency, and coloration. Polymers that have been subject to such incorporations are sometimes referred to as formulated polymers. These formulated polymers are generally in the form of small pellets until they are actually used to make products.
A certain quantity of unused formulated polymers may be discarded to a recycle stream during a molding process, or other process used to make the polymer products. Inclusion of a formulated polymer into a recycle stream often occurs when the polymer is in excess of that needed for the product or if the polymer is remaining trim from the product after molding. Additionally, commercial, industrial, and other consumers discard products containing formulated polymers following the useful life of the products. Once discarded, formulated polymers may be recycled and reused in other products. Because a large volume of polymers used in commercial, industrial, and consumer products are eventually discarded, polymer recycling and recovery is desirable for conservation of natural resources and other environmental considerations. However, current polymer recycling processes do not completely restore formulated polymers to their pure, clean unformulated state, because formulated polymers are not easily separated from their additives. Thus, even after current recycling techniques, many formulated polymers continue to contain many of the same additives as contained in previous formulation packages. Accordingly, subsequent uses of formulated polymers require increased additives for use in association with a new formulation package to hide the original formulation package. These further formulated polymers exhibit increasingly unpredictable characteristics caused by the increased use of additives, and polymer reprocessing becomes increasingly difficult and limited. Continued reformulation of previous formulations causes degradation of the products for which the polymers may be used. As this degradation of use is repeated, the polymer's properties also erode as the additives increase. Eventually, the polymer will have little or no value in the marketplace.
Therefore, while an unformulated polymer has almost unlimited applications, initial formulation of that polymer limits subsequent applications, and reformulation of the initial formulation limits applications even further. By way of example, consider a clear polymer substantially free of formulations such that the polymer is used to make window glazing. Following the useful life of the window glazing, the polymer is recycled and designated for re-use in a tan colored article. Before the polymer is used in the tan colored article, the polymer must be formulated to give the polymer the appropriate article characteristics, e.g., tan coloration. Following recycling of the tan colored article, attempted re-use of the now formulated polymer might be limited to applications for brown articles. Additional reprocessing of the polymer may further limit potential polymer applications such that the polymer might only be used to make black articles, or articles of some other color that will hide the brown.
Accordingly, it would be of advantage if the polymer recycling process could completely separate all additives from a polymer (i.e., deformulate the polymer) with little, if any, loss in the original chemical and physical properties of the polymer. Such deformulated polymers could then be re-used in any products and in any manner appropriate for use of the original polymer. For example, the black articles in the above illustration could be deformulated and used again as a window glazing. With an increased number of applications available for the recycled polymer, demand for the polymer would increase along with the value of the polymer.
Some prior art processes disclose techniques for separating or recycling plastics such as U.S. Pat. No. 5,278,282 to Nauman et al. Nauman et al. involves mixing commingled plastics with a solvent at various temperatures, and extracting certain polymers from the solution at particular temperatures. Nauman filters any contaminates from the solution which are not dissolved by the solvent. However, this process fails to remove all additives from the polymers. Therefore, although the polymers are separate at the conclusion of the Nauman process, the polymers are still formulated, i.e., still contain some additives.
Similarly, U.S. Pat. No. 5,269,948 to Krutchen discloses a process for purifying waste contaminated polystyrene by dissolving the polystyrene in a solvent to form a solution, and recovering the contaminate free solution. However, the Krutchen process only discloses removal of accumulated waste products such as dirt and food particles, it does not disclose removal of any additives included in the original polystyrene product.
Accordingly, there is a need in the industry for a process which will remove additives such as pigments and dyes from polymers and result in an unformulated polymer that may be used in the same manner as the original unformulated polymer.